Microorganisms are essential for human life. Microorganisms decompose the carbon compounds in dead animals and plants and convert them into carbon dioxide. Intestinal bacteria assist in food digestion. Some vitamins are produced by bacteria that live in the intestines. Sewage and industrial wastewater are treated by activated sludge composed of microbial communities. All of these are due to the ability of microbes to produce many enzymes that can degrade chemicals. How do teachers make students understand that microorganisms are always associated with humans, and that microorganisms have the ability to degrade chemicals? The presence of microorganisms on humans can be shown by incubating agar plates after they are touched by the hands of students. The ability of microorganisms to degrade chemicals can be shown by an analytical measurement of the degradation of chemicals. When the chemicals are dyes (colorants) in water, microbial activity on degradation of dyes can be demonstrated by observing a decreasing degree of color as a result of the enzymatic activity (e.g., azoreductase). Dyes are widely used in the textile, food, and cosmetic industries. They are generally resistant to conventional biological wastewater treatment systems such as the activated sludge process (4). The discharge of wastewater containing dye pollutes surface water. The ability of microorganisms to decolorize and degrade dyes has been widely investigated to use for bioremediation purposes (5). The goal of this tip is to understand the presence of bacteria on human skin and the ability of bacteria to degrade colorant chemicals (decolorization). In this tip, students first cultivate and isolate bacteria on their hands, and then examine potential decolorization activity of each bacterium by observing the degree of color of the liquid in tubes in which bacteria isolated from students’ hands were inoculated. Decolorization activity of bacterial isolates from human skin has been reported recently (6). To date this author has frequently obtained colorant-degrading bacterial isolates from human hands as a result of work on a scientific education project. This tip does not require analytical measurements. Students can examine a number of bacterial isolates simultaneously. Therefore, it is appropriate for high school and introductory level college courses.